1. Field of the Invention
The invention relates to a caoutchouc mixture for the manufacture of rubber products (vulcanizates) with low-temperature application capability even under extreme climatic conditions, resistance to oil, low crystallization tendency and high dynamic stressability, on the basis of natural caoutchouc and the usual mixing ingredients such as fillers, plasticizers, anti-aging agents, cross-linking agents, zinc oxide, as well as additional additives, if necessary.
2. The Prior Art
When passenger cars for long-distance travel are shipped to the former Soviet Union, operators there request that each second passenger car is equipped with a 32-kw power generator set (power for air-conditioning in cold weather). Each of said power generator sets comprises an axle center transmission (with two rubber couplings; so-called rubber centering cone couplings), a universal-joint shaft, a highly elastic rubber preshift coupling, and a generator. The rubber preshift coupling connects the universal-joint shaft with the generator. The long-distance passenger cars with the above power generator set and, therefore, also the rubber couplings have to be capable of functioning even at outside temperatures of -60.degree.. The rubber materials of the coupling should crystallize as little as possible. In addition to such strong influence of cold, an influence of oil occurs in connection with the rubber preshift couplings when the car is cleaned, which, however, must not be viewed as permanent. Heretofore, no suitable rubber materials have been available to meet at the same time said requirements with respect to low-temperature application capability, resistance to oil, low crystallization tendency and high dynamic stressability.
In the preparation of a caoutchouc mixture from various types of elastomer, its compatibility in the polymer blend has to be taken into account. If vulcanizate properties are required which no elastomer alone can satisfy, it is important that a thermodynamically compatible elastomer blend is available that optimally possesses all of the required properties. The use of such a caoutchouc mixture then represents a compromise solution. In addition, such a polymer blend has to be capable of cross-linking.
Cross-linked caoutchouc mixtures on the basis of natural caoutchouc are known, whereby reference is made, for example, to the following literature sources: U.S. Pat. No.3,342,660; BE-A-698 519; GB-A-2 004 286; Chemical Patents Index, Documentation Abstracts Journal (Section Ch, Week 9128, Sep. 11, 1991, Derwent Publications Ltd., London, GB, page 412, AN 91-203 142). However, the caoutchouc mixtures known heretofore do not satisfy the overall requirements. For example, a caoutchouc mixture is introduced in the last-mentioned document Chemical Patents Index, which contains epoxidized natural caoutchouc and is suitable for application in the low-temperature range, without, however, satisfying all requirements.